Error after installation when trying to activate

Parse error: syntax error, unexpected '[' in /home2/hismynx/public_html/wp-content/plugins/tesla-login-customizer/tt_login/admin/Option.php on line 33

Line 33 is part of an array being defined:

function __construct(array $args, Tab $parent_tab, array $custom_vars, array $dependencies){
     24         $this->parent_tab = $parent_tab;
     25         $this->args = array(
     26             'id'                => $this->prefix( $args[0] ),
     27             'title'             => $args[1],
     28             'type'              => $args[2],
     29             'std'               => isset($args[3]) ? $args[3] : NULL,
     30             'descr'             => isset($args[4]) ? $args[4] : NULL,
     31             'value'             => isset($args[5]) ? $args[5] : NULL,
     32             'placeholder'       => isset($args[6]) ? $args[6] : NULL,
     33             'classes'           => isset($args[7]) ? $args[7] : [],
     34             'options_group_id'  => $this->parent_tab->slug
     35         );

The offending line is the ‘classes’, seems not to like the [] at the end.

The error occured when I loaded the plugin from the plugins page. I then deleted the plugin and downloaded it from wordpress.org and uploaded the zip file – same result.

https://wordpress.org/plugins/tesla-login-customizer/